Straight trucks and tractor-trailers (hereinafter referred to as “vehicles”) frequently transport cargo that must be maintained at a predetermined temperature during transportation in order to preserve the quality of the cargo. Vehicles that transport such temperature-sensitive cargo have a conditioned space that is maintained at a predetermined temperature by a temperature control unit mounted to the vehicle at a location either on the front of the cargo box or underneath the cargo box. These temperature control units are respectively referred to as nosemount and undermount transport temperature control units.
Undermount units are used when vehicle tilt cab clearance cannot be provided by a nosemount unit, when a nosemount unit cannot be provided for a drawbar trailer, or when the weight of a nosemount unit causes the vehicle to become unstable. Some countries, including Japan, have specific regulations mandating the use of undermount temperature control units under certain circumstances.
An undermount temperature control unit has three basic parts—a condenser module located underneath the cargo box, an evaporator module located inside the cargo box, and an installation kit that connects these modules. When the undermount temperature control unit is electrically powered, it also has a fourth part—an auxiliary alternator located in the vehicle's engine compartment. The auxiliary alternator is connected to a control box that is typically housed in the condenser module.